Note that the described null hypothesis directly takes into account the heterogeneity of countries with respect to the total value of goods traded. For each pair of countries, we separately evaluate the p-value and then use a cutoff (\(\widetilde{p}\) ) to select only those links that represent a significant departure from the hypergeometric benchmark. The resulting matrices are then dichotomized.The hypergeometric multi-urn benchmark is equivalent to the Monte Carlo degree-preserving network rewiring procedure [1]}.
